Science Fiction Problems: Cloaking and Invisibility
Posted by erikthereddest
Hello all! This week’s a big one on a topic that’s been slowly building in my brain for some time now: cloaking. Whether it’s your run-of-the-mill Klingon Warbird or practically every cyberpunk anime ever created, someone somewhere is going invisible. Is this possible? Is this practical? Does it matter?
Yes. Sometimes. Absolutely! Let me show you how.
Set Ship to “Invisible Mode”
Ok, here’s my first problem: you don’t need to be invisible in space. Chances are, if we ever do get to where we regularly traipse around the galaxy in our very own star cruisers, we won’t be relying on sight to pick out that tiny speck against the black of the infinite vacuum that may or may not be a pirate vessel bent on shivering your timbers and whatnot. It doesn’t matter if the ship’s painted bright neon orange- unless it’s about as big as a small moon, you’re not going to notice it from 1000 miles away in space.
Sure, you could outfit your ship with hundreds of ultra-powerful telescopic cameras to let your on-board computers pick out suspicious objects in space, but there are other MUCH more effective methods which I’ll likely discuss in a later post. The gist of it is that depending on how space ships move around in your story, they’re going to emit all sorts of waves of radiation, heat, and light that could be used to pinpoint their location, in much the same way we do so with other things in space (planets, stars, asteroids, etc.).
If a ship wanted to be “cloaked”, all it would need to do is contain its heat/radiation/exhaust/whatever so that other ships that rely on detecting those things wouldn’t be able to. If the hidden ship did need to get close, a simple jet-black paint job would get him about as close as he could risk without being detected by other forms of sensors.
Some science fiction story worlds have taken this issue into account, one great example of which is seen in the sci-fi RPG video game Mass Effect, by Bioware. The Normandy (seen right), a human vessel designed as an elite stealth frigate, uses such a system to conceal its radiation and heat signature inside its insulated hull, rendering it practically invisible to anyone they might need to sneak up on.
If you really want to, you could come up with some specific instances where your ships would need to be completely invisible, but as you can see, it’s not as generally useful as you might think. Not to say that other things in space wouldn’t find it tactically relevant to make themselves invisible, but it would all have to be in addition to the kind of shielding described above. That way, the rebels can have their ultra-secret home base orbiting a mysterious gas planet- they’re just going to need a little more than a cloaking field.
Where it would in fact be incredibly useful is on the ground- soldiers, elite commandos, buildings, vehicles, you name it! Practically anything not in space would be close enough to its observers to make use of some good ‘ol fashioned invisibility.
It’s Just Magic, OK??
If only it was that simple. Sure, fantasy stories have the easy, no-questions-asked solution to the glaring problem of exactly how that particular article of clothing lets it wearer run around unseen, but if a sci-fi author wants anything similar, he has to WORK for it to be believable. Obviously TV and movies again get a bit of a pass here as long as the CGI department does its job, but if you want your invisible soldiers to feel like more than a convenient plot point, you’ll need some kind of tech basis for your cloaking device.
Since sci-fi writers don’t have access to some mystical veil that makes the wearer transparent, we have one of two methods available to us: optical camouflage or metamaterials.
In a certain sense, we already have the technology to render someone invisible. Specially-designed patterns printed on clothing can diffuse the shape of a human into the background, and artificial leaves and other faux foliage woven into a suit can make a man impossible to find. Usually, becoming invisible is only really useful if your opponent is unaware of you- for snipers, it doesn’t make much difference if their gunshot reveals their location if their target is already dead. If you want to move unseen, however, camouflage can only help you so much.
As is the case in many areas of science, however, Nature has already done what we can only dream of. Cephalopods (octopi, cuttlefish, etc.) are capable of what is called Adaptive Camouflage, or camouflage that is able to change based on its background. The octopus is so adept at this that it can almost perfectly replicate the pattern and contrast of his environment:
See what I mean? How does he do it? No one quite knows, but we’ve been trying to do something similar for quite some time. What do we have so far? Well, this:
Kind of embarrassing, isn’t it? The basic means we have at our disposal is by using a camera to take in the image of the environment behind an object, and then projecting that image in front of it by some method. The effect is similar to invisibility, in that the observer can see through to the other side of the object, but of course it’s far from perfect. The folks at the Inami Laboratory break it down into an external projector and a reflective material (which seems like it would be inconvenient), but another way would be to use small screens to display the image being taken in by the camera. By setting up an array of cameras pointing in every direction, each display could then handle every angle, making it so that no matter what perspective an observer has on the user, the effect remains.
One similar idea is being done for BAEs ACTIV technology, but for infrared instead of visible light. Each hexagonal panel can heat or cool itself to match the background and blend in, making the heat signature of the tank indeterminable. If you did the same thing but with individual display screens, you could have something resembling Adaptive Camouflage. While this technology seems pretty basic at the moment, it is rapidly becoming more sophisticated and practical. In either case, there are Pros and Cons to consider:
- Compatible with armor: screens could be built from nano-scale pixels built into the top layer of armor plating, or placed behind layers of transparent metals, allowing for both protection and camouflage.
- Light weight and comparatively cheap. While the components of such a system would be tricky to manufacture, they would be comparatively cheaper and less bulky than the Metamaterials described below, and considerably more durable. If the surface was scratched, the image would just have a small blemish instead of just failing completely. What’s more, that small piece could be easily replaced.
- Not true invisibility: while this method would allow for some pretty convincing camouflage that changes on the fly, it would still be quite possible to detect the user with normal equipment. Microwaves and other detecting light beams would still bounce off of the surfaces of the cloaked object, and with certain conditions (dust, rain, mud, etc.), the user could become easily visible to the naked eye as well.
- Blur effect: Just as it works better for normal camouflage to be still, so would this optical camouflage work better if the user didn’t move. If he decided he needed to run for it, however, the effect would remain, but there would always be a danger that his movements would be faster than his on-board computer could refresh the screens of the system, creating a flicker or blurring effect. This effect could make it fairly easy to pick out a cloaked figure or vehicle, rendering the device almost useless.
Since the human eye works by absorbing the light waves bounced off of objects, if you somehow managed to make light bend around something, it would become invisible. An example of this is a mirage- the illusion of pools of shimmering water on the ground at a distance. This occurs when light shining across a surface distant from your vantage point bends over the horizon, obscuring the ground with a reflection of the sky. The ground is essentially being made invisible by the waves of light that are bending around it, so you see the sky where the ground should be.
Researchers at Duke University managed to replicate this effect using intricately woven structures of exotic metals by generating just the right electromagnetic fields to divert light waves around an object (in this case, a small bump in the surface. The result is that a wide range of light waves (including some not in the visible spectrum) simply move around the bump instead of bouncing off of it, rendering it invisible.
Now that all sounds cool and everything, but the truth is its all on the micro-scale right now. Doing this on a larger, more useful scale is pretty far off at the moment, but they’re working on it, and that’s good enough for us. These devices could potentially be made to work off of one another, passing light waves off to bend around a surface (like a jumpsuit, or the armor of a tank), but it’s all very delicate. Alternately, the device could just be super-sized, but then it would be extremely heavy and not very mobile. There are a number of other Pros and Cons associated with this method:
- Adaptability: This technology could be used not only to make objects invisible, but to mask them from radio waves, infrared, and any other light waves that could be used to detect it or carry a signal. It could also be used to redirect sound waves, and even seismic waves of energy carried through the ground.
- This method, if successful, would be an absolute solution. It would not be an illusion, but an actual nullification of light-based senses in any spectrum. On top of that, in contrast to Optical Camouflage, metamaterials could be effective in spite of movement, at any speed slower that the speed of light.
- Expensive and fragile. The exotic metals and intricate patterns required for this process would require extensive manufacturing with specialized equipment, and once it’s built, you can’t just slap some armor on it. Any sort of plating or traditional armor would disrupt the effect, and the metamaterials are fragile and intricate so that they could not work properly if damaged. You could put armor under the layer of metamaterials, but if the user is exposed because his invisibility field blinked out, that armor probably won’t be enough.
- Distortion: while this wouldn’t be an issue if your system was just an upsized version of the metamaterials, if its made up of a composite of a bunch of little devices in order for it be mobile, as in the case of a personal suit or small vehicle, there would likely be some distortion as the pieces move and shift. The effect would probably not be a problem unless the wearer is already known and the enemy is actively looking for the tell-tale blur, but it is a consideration (and a potential plot point! Gosh I love those).
This method is a bit more like the traditional cloaking that we see everywhere (which kind of makes it even cooler since its a real technology), but it’s also the cleanest. This method is better used in moderation due to the potential plot holes that could arise if this sort of technology is easy to get at, but if you want a way to have invisibility without the problems associated with Optical Camouflage, metamaterials are the way to go.
About erikthereddestI'm a Masters student in English, and I love technology and Science Fiction. I am refining and enhancing my (admittedly novice) writing talents under the sage advice of my friends here at Lantern Hollow Press, and with the great many books I am reading from the best authors I can find.
Posted on September 28, 2011, in Cliches, Erik Marsh, Inspiration, Lantern Hollow Press Authors, Science Fantasy, Science Fiction, science fiction problems, Star Trek, Universes, World Creation, Writing Hints and Helps and tagged cloaking, cloaking device, How to Write Science Fiction and Fantasy, invisibility, science fantasy, science fiction, science fiction problems, writing science fiction. Bookmark the permalink. 6 Comments.